Variance Metric: Difference between revisions

** QUOTE: In [[probability theory]] and [[statistics]], the '''variance</B> is a measure of how far a set of numbers is spread out. It is one of several descriptors of a [[probability distribution]], describing how far the numbers lie from the [[mean]] (expected value). In particular, the variance is one of the [[Moment (mathematics)|moments]] of a distribution. In that context, it forms part of a systematic approach to distinguishing between probability distributions. While other such approaches have been developed, those based on [[Moment (mathematics)|moments]] are advantageous in terms of mathematical and computational simplicity.    <P>  The variance is a [[population parameter|parameter]] describing in part either the actual probability distribution of an observed population of numbers, or the theoretical probability distribution of a sample (a not-fully-observed population) of numbers. In the latter case a sample of data from such a distribution can be used to construct an estimate of its variance: in the simplest cases this estimate can be the '''sample variance''', defined below.